Why in rewriting the onsize function will first call the base class CDialog: : onsize, and I see some rewriting onsize interface, just call a CDialog: : onsize, and didn't do other operation, in this case, why want to rewrite the onsize function, not have inherited the onsize interface, direct use of no, CDialog in MFC: : onsize interface to realize the function of what? Is it allocated the coordinates of the window